We’ve done lots of different holidays with them, and now the kids are 16/18 and say their favourite holidays were:
1.) Devon/Somerset when we rent a house with all the uncles, aunties and cousins
2.) Norway (hiking, swimming in lakes, having a bbq picnic on walks) with uncle and auntie
3.) Barcelona (rooftop pool, wandering around a lot, nice food, people were nice, but I gather they are now sick of tourists in Barcelona. This was 19 yrs ago)
What did not feature was Indonesia, Mexico and Vietnam (ie our bigger trips) (they remember being too hot, jellyfish, mosquitos and other bugs, being in hospital with food poisoning/dehydration)
Devon is the firm favourite, because of the cousins and uncles, about playing rounders and visit beaches in storms
So for kids, it’s not about location and luxury/adventure/historic buildings/museums. It was all about people to share it with.